Wind turbines are increasingly gaining importance in the area of renewable sources of energy generation. Wind turbine technology is now the basis of large scale power generation applications. Of the many challenges that exist in harnessing wind energy, one challenge is maximizing wind turbine performance while minimizing system loads in given wind conditions. Non-limiting examples of improved wind turbine performance parameters include maximized aerodynamic efficiency, maximized energy output, minimized wind turbine system loads, minimized noise, and combinations thereof. Improvement in these parameters may lead to a minimized cost of energy and other benefits.
One issue in optimizing the performance parameters is flow separation over the wind turbine blades. Flow separation may lead to stall, which is a limiting factor in wind turbine blade design. When stall occurs, lift generated by the blades may decrease significantly and a large component of the torque, which is the driving force imparted by the wind to the wind turbine, may be lost. Solutions that provide an ability to control flow separation, i.e., diminish or delay the separation, may allow the wind turbine blades to maximize lift.
Currently, there is no efficient method to measure directly the flow fields across portions of the wind turbine blade. All fine aerodynamic rotor controls are done via loads and deflections imposed by aerodynamic forces as substitutes for direct measurement of the flow field. Moreover, there is little or no resolution finer than a whole blade. Prior measurement attempts have used flow visualizations using oil flow techniques, cameras mounted on the blade or hub, or angle of attack instruments. These short term methods, however, are not suitable for continuous use in the field as a part of an automated control system, particularly in severe or dirty operating environments and the like.
There is a desire therefore for an improved wind speed measurement techniques along the length of a blade. The use of such measurements should provide increased performance and efficiency.